diff --git a/pkgs/development/libraries/opencsg/default.nix b/pkgs/development/libraries/opencsg/default.nix
index 1fdddf930cf..724c0d7c764 100644
--- a/pkgs/development/libraries/opencsg/default.nix
+++ b/pkgs/development/libraries/opencsg/default.nix
@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
 
   preConfigure = ''
     rm example/Makefile src/Makefile
-    qmakeFlags="$qmakeFlags INSTALLDIR=$out"
+    qmakeFlags=("''${qmakeFlags[@]}" "INSTALLDIR=$out")
   '';
 
   postInstall = ''